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Abstract:

A controller (10) for controlling a process nozzle (20) and a laser
oscillator (22) includes: an analyzer (12); a calculator (13) for
calculating angle of a virtual corner part formed by two main process
paths; a determining unit (14) for determining whether distance between
the two main process paths corresponding to the circular-arc process
path(s) is smaller than a first predetermined value, and determining
whether the calculated angle is smaller than a second predetermined
value; and a changing unit (15) for changing a laser process condition in
the circular-arc process path(s) from a laser process condition in the
main process paths when it is determined that the linear distance is
smaller than the first predetermined value and the angle is smaller than
the second predetermined value.

Claims:

1. A controller for controlling a process nozzle and a laser oscillator
to process a workpiece along a process path determined according to a
process program, comprising: an analyzer for analyzing two main process
paths which are adjacent to each other and one or plural circular-arc
process paths or linear process paths continued to both of the main
process paths on the basis of the process program; a calculator for
calculating angle of a virtual corner part formed by the two main process
paths; a determining unit for determining whether or not linear distance
between the two main process paths corresponding to the circular-arc
process path(s) or linear process path(s) or distance along the
circular-arc process path(s) or linear process path(s) is equal to or
less than a first predetermined value, and determining whether or not the
angle calculated by the calculator is equal to or less than a second
predetermined value; and a changing unit for changing a laser process
condition in the circular-arc process path(s) or linear process path(s)
from a laser process condition in the main process paths when the
determining unit determines that the linear distance or the distance
along the circular-arc process path(s) or linear process path(s) is equal
to or less than the first predetermined value and the angle is equal to
or less than the second predetermined value.

2. The controller according to claim 1, wherein the changing unit sets a
laser process condition in a part of the main process path extending from
the circular-arc process path or the linear process path along the main
process path by predetermined distance to the changed laser process
condition in the circular-arc process path or linear process path.

3. The controller according to claim 1, wherein the changing unit sets
the laser process condition in a part of the main process path extending
from the circular-arc process path or the linear process path along the
main process path by predetermined distance so as to be different from
the laser process condition in the circular-arc process path or the
linear process path and the laser process condition in the main process
paths.

4. The controller according to claim 1, wherein at least one of speed of
the process nozzle and an output of the laser oscillator in the laser
process condition changed by the changing unit is set to be smaller than
the speed of the process nozzle and the output of the laser oscillator in
the laser process condition in the main process path.

5. The controller according to claim 1, wherein the changing unit changes
the laser process condition so as to temporarily stop operation of the
process nozzle in at least one of start and termination points of the
circular-arc process path or linear process path or in a part of the main
process path extended by predetermined distance along the main process
path from the circular-arc process path or linear process path.

6. The controller according to claim 1, wherein the changing unit changes
the laser process condition so as to temporarily stop an output of the
laser oscillator in at least one of start and termination points of the
circular-arc process path or linear process path or in a part of the main
process path extended by predetermined distance along the main process
path from the circular-arc process path or linear process path.

7. The controller according to claim 5, wherein after the operation of
the process nozzle is temporarily stopped, the changing unit changes the
laser process condition so as to perform a piecing operation.

8. A control method of controlling a process nozzle and a laser
oscillator to process a workpiece along a process path which is
determined according to a process program, comprising the steps of:
analyzing two main process paths which are adjacent to each other and one
or plural circular-arc or linear process paths continued to both of the
main process paths on the basis of the process program; calculating angle
of a virtual corner part formed by the two main process paths;
determining whether or not linear distance between the two main process
paths corresponding to the circular process path or linear process path
or distance along the circular-arc process path or linear process path is
equal to or less than a first predetermined value and determining whether
or not the calculated angle is equal to or less than a second
predetermined value; and changing a laser process condition in the
circular-arc process path or linear process path from a laser process
condition in the main process paths when it is determined that the linear
distance or the distance along the circular-arc process path or linear
process path is equal to or less than the first predetermined value and
the angle is equal to or less than the second predetermined value.

9. The control method according to claim 8, wherein the laser process
condition in a part of the main process path extending from the
circular-arc process path or linear process path along the main process
path by predetermined distance is set to the changed laser process
condition in the circular-arc process path or linear process path.

10. The control method according to claim 8, wherein the laser process
condition in a part of the main process path extending from the
circular-arc process path or linear process path along the main process
path by predetermined distance is set so as to be different from a laser
process condition in the circular-arc process path or the linear process
path and a laser process condition in the main process paths.

11. The control method according to claim 8, wherein at least one of
speed of the process nozzle and an output of the laser oscillator in the
changed laser process condition is set to be smaller than speed of the
process nozzle and output of the laser oscillator in the laser process
condition in the main process path.

12. The control method according to claim 8, wherein the laser process
condition is changed so as to temporarily stop the operation of the
process nozzle in at least one of start and termination points of the
circular-arc process path or linear process path or in a part of the main
process path extended by predetermined distance along the main process
path from the circular-arc process path or linear process path.

13. The control method according to claim 8, wherein the laser process
condition is changed so as to temporarily stop an output of the laser
oscillator in at least one of start and termination points of the
circular-arc process path or linear process path or in a part of the main
process path extended by predetermined distance along the main process
path from the circular-arc process path or linear process path.

14. The control method according to claim 12, wherein after the operation
of the process nozzle is temporarily stopped, the laser process condition
is changed so as to perform a piecing operation.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates to a controller for processing a
corner part in a process path.

[0003] 2. Description of Related Art

[0004] Generally, in a laser cutting process, the cutting direction is
changed to generate a corner part (edge part). As the angle of the corner
part becomes acuter, heat applied from a laser becomes excessive. A
process failure may occur due to melted matter (dross) or self-burning,
and as a result an uncuttable state occurs.

[0005] To suppress heat applied to a corner part (edge part), there is a
case that a laser output is temporarily stopped in a corner part to
provide cooling time and laser pulses are output (edge process) at the
time of restarting the cutting after the cooling time. Alternatively, an
operation (switch-back operation) is performed, of cutting a corner part
from the vertex only by predetermined distance, temporarily stopping a
laser output to have time of cooling the cut part, after the cooling,
moving the laser output backward in the cut process path to the vertex of
the corner part, and restarting the cutting along the process path.
Whether such a process is performed or not is determined according to the
angle formed in the corner part. Usually, a controller used in the laser
cutting process analyzes a process path and makes the decision.

[0006] Japanese Patent No. 3,211,902 discloses a processing method of edge
processing in accordance with the angle of a corner part generated by two
cutting paths. Japanese Patent No. 3,825,123 discloses a process method
and a controller, in the case of cutting the outside of an acute corner
part, edge processing by analyzing the angle of the corner part of paths
instructed by a process program, not actual process paths.

[0007]FIG. 12 is a diagram showing a corner part constructed by two
linear main process paths in a related art. As shown in FIG. 12, an angle
θ1 is generated between two linear main process paths ab and bc. In
the case of cutting so as to obtain a relatively acute-angled corner
part, by analyzing the two process paths ab and bc, the angle θ1
can be obtained.

[0008]FIG. 13 is a diagram showing a corner part constructed by two
linear main process paths and a circular-arc path in a related art. In
FIG. 13, a small circular-arc path ef is inserted between two linear
paths de and fg. Due to the circular-arc path ef, a smooth, rounded
corner part is formed.

[0009] However, in the case shown in FIG. 13, a controller recognizes an
angle θ2 generated between the cut path de in front of the
rounded-corner part and a tangent line eh at the point "e" on the
circular-arc path ef. As understood from FIG. 13, the angle θ2 is
an obtuse angle. In other words, the controller determines a part having
a relatively acute angle in a shape to be cut as an obtuse-angle part. In
such a case, the edge process cannot be performed properly.

[0010] Further, Japanese Patent Nos. 3,211,902 and 3,825,123 are limited
to the case where a corner part to be cut has an acute angle formed by
two linear main process paths. Consequently, the techniques disclosed in
Japanese Patent Nos. 3,211,902 and 3,825,123 cannot be applied to a
corner part obtained by inserting a small circular-arc path or a small
linear path between two linear main process paths.

[0011] The present invention has been achieved in view of such
circumstances and an object of the invention is to provide a controller
capable of properly processing a corner part even in the case where a
small circular-arc path or a small linear path is inserted between two
main process paths.

SUMMARY OF THE INVENTION

[0012] To achieve the object, according to a first mode, there is provided
a controller for controlling a process nozzle and a laser oscillator to
process a workpiece along a process path determined according to a
process program, including: an analyzer for analyzing two main process
paths which are adjacent to each other and one or plural circular-arc
process paths or linear process paths continued to both of the main
process paths on the basis of the process program; a calculator for
calculating angle of a virtual corner part formed by the two main process
paths; a determining unit for determining whether or not linear distance
between the two main process paths corresponding to the circular-arc
process path(s) or linear process path(s) or distance along the
circular-arc process path(s) or linear process path(s) is equal to or
less than a first predetermined value, and determining whether or not the
angle calculated by the calculator is equal to or less than a second
predetermined value; and a changing unit for changing a laser process
condition in the circular-arc process path(s) or linear process path(s)
from a laser process condition in the main process paths when the
determining unit determines that the linear distance or the distance
along the circular-arc process path(s) or linear process path(s) is equal
to or less than the first predetermined value and the angle is equal to
or less than the second predetermined value.

[0013] According to a second mode, in the first mode, the changing unit
sets a laser process condition in a part of the main process path
extending from the circular-arc process path or the linear process path
along the main process path by predetermined distance to the changed
laser process condition in the circular-arc process path or linear
process path.

[0014] According to a third mode, in the first mode, the changing unit
sets the laser process condition in a part of the main process path
extending from the circular-arc process path or the linear process path
along the main process path by predetermined distance so as to be
different from the laser process condition in the circular-arc process
path or the linear process path and the laser process condition in the
main process paths.

[0015] According to a fourth mode, in the first mode, at least one of
speed of the process nozzle and an output of the laser oscillator in the
laser process condition changed by the changing unit is set to be smaller
than the speed of the process nozzle and the output of the laser
oscillator in the laser process condition in the main process path.

[0016] According to a fifth mode, in the first mode, the changing unit
changes the laser process condition so as to temporarily stop operation
of the process nozzle in at least one of start and termination points of
the circular-arc process path or linear process path or in a part of the
main process path extended by predetermined distance along the main
process path from the circular-arc process path or linear process path.

[0017] According to a sixth mode, in the first mode, the changing unit
changes the laser process condition so as to temporarily stop an output
of the laser oscillator in at least one of start and termination points
of the circular-arc process path or linear process path or in a part of
the main process path extended by predetermined distance along the main
process path from the circular-arc process path or linear process path.

[0018] According to a seventh mode, in the fifth mode, after the operation
of the process nozzle is temporarily stopped, the changing unit changes
the laser process condition so as to perform a piecing operation.

[0019] According to an eighth mode, there is provided a control method of
controlling a process nozzle and a laser oscillator to process a
workpiece along a process path which is determined according to a process
program, including the steps of: analyzing two main process paths which
are adjacent to each other and one or plural circular-arc or linear
process paths continued to both of the main process paths on the basis of
the process program; calculating angle of a virtual corner part formed by
the two main process paths; determining whether or not linear distance
between the two main process paths corresponding to the circular process
path or linear process path or distance along the circular-arc process
path or linear process path is equal to or less than a first
predetermined value and determining whether or not the calculated angle
is equal to or less than a second predetermined value; and changing a
laser process condition in the circular-arc process path or linear
process path from a laser process condition in the main process paths
when it is determined that the linear distance or the distance along the
circular-arc process path or linear process path is equal to or less than
the first predetermined value and the angle is equal to or less than the
second predetermined value.

[0020] According to a ninth mode, in the eighth mode, the laser process
condition in a part of the main process path extending from the
circular-arc process path or linear process path along the main process
path by predetermined distance is set to the changed laser process
condition in the circular-arc process path or linear process path.

[0021] According to a tenth mode, in the eighth mode, the changing unit
sets the laser process condition in a part of the main process path
extending from the circular-arc process path or linear process path along
the main process path by predetermined distance so as to be different
from a laser process condition in the circular-arc process path or the
linear process path and a laser process condition in the main process
paths.

[0022] According to an eleventh mode, in the eighth mode, at least one of
speed of the process nozzle and an output of the laser oscillator in the
changed laser process condition is set to be smaller than speed of the
process nozzle and output of the laser oscillator in the laser process
condition in the main process path.

[0023] According to a twelfth mode, in the eighth mode, the laser process
condition is changed so as to temporarily stop the operation of the
process nozzle in at least one of start and termination points of the
circular-arc process path or linear process path or in a part of the main
process path extended by predetermined distance along the main process
path from the circular-arc process path or linear process path.

[0024] According to a thirteenth mode, in the eighth mode, the laser
process condition is changed so as to temporarily stop an output of the
laser oscillator in at least one of start and termination points of the
circular-arc process path or linear process path or in a part of the main
process path extended by predetermined distance along the main process
path from the circular-arc process path or linear process path.

[0025] According to a fourteenth mode, in the twelfth mode, after the
operation of the process nozzle is temporarily stopped, the laser process
condition is changed so as to perform a piecing operation.

[0026] The above and other objects, features, and advantages of the
present invention will become more apparent from the detailed description
of typical embodiments of the present invention shown in the appended
drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0027]FIG. 1 is a schematic diagram of a laser system including a
controller based on the present invention.

[0028]FIG. 2 is a flowchart showing operation of the controller based on
the present invention.

[0029]FIG. 3A is a diagram showing a corner part constructed by two
linear main process paths and a circular-arc path in the invention.

[0030]FIG. 3B is a diagram showing a corner part constructed by two
linear main process paths and a linear path in the invention.

[0031]FIG. 4A is a diagram showing the relations among time, process
nozzle feed speed, and laser output in an embodiment.

[0032]FIG. 4B is a diagram showing the relations among time, process
nozzle feed speed, and laser output in another embodiment.

[0034]FIG. 5B is a diagram showing a second example of the corner part.

[0035]FIG. 6A is a diagram showing a third example of the corner part.

[0036]FIG. 6B is a diagram showing a fourth example of the corner part.

[0037]FIG. 7A is a diagram showing a fifth example of the corner part.

[0038]FIG. 7B is a diagram showing a sixth example of the corner part.

[0039]FIG. 8A is a diagram showing a seventh example of the corner part.

[0040]FIG. 8B is a diagram showing an eighth example of the corner part.

[0041] FIG. 9 is a diagram showing a ninth example of the corner part.

[0042] FIG. 10A is a diagram showing a tenth example of the corner part.

[0043] FIG. 10B is a diagram showing an eleventh example of the corner
part.

[0044]FIG. 11 is a diagram similar to FIG. 4A, showing the relations
among time, process nozzle feed speed, and laser output in an additional
embodiment.

[0045]FIG. 12 is a diagram showing a corner part constructed by two
linear main process paths in a conventional technique.

[0046]FIG. 13 is a diagram showing a corner part constructed by two
linear main process paths and a circular-arc path in a conventional
technique.

DETAILED DESCRIPTION

[0047] Hereinafter, embodiments of the present invention will be described
with reference to the appended drawings. In the following drawings,
similar reference numerals are designated to similar members. For easier
understanding, the scale of the drawings is properly changed.

[0048]FIG. 1 is a schematic diagram of a laser system including a
controller based on the present invention. As shown in FIG. 1, a
controller 10 is connected to a servo motor 21 for moving a process
nozzle 20 along a surface of a fixed workpiece W, and a laser oscillator
22 oscillating a laser beam output from the process nozzle 20. The laser
oscillator 22 is a relatively-high-output laser oscillator of a discharge
excitation type and is, for example, a carbon dioxide laser whose output
is 1 kW or higher. A configuration that the process nozzle 20 is fixed
and the servo motor 21 moves the workpiece W may be also employed.

[0049] The controller 10 is a digital computer and functions as a process
program 11 for processing the workpiece W, an analyzer 12 for analyzing a
process on the workpiece W on the basis of the process program 11, and a
calculator 13 for calculating the angle of a virtual corner part formed
by two main process paths adjacent to each other and analyzed by the
analyzer 12.

[0050] The controller 10 also functions as a determining unit 14 for
determining whether a linear distance between the two main process paths
or a distance along the circular-arc or linear process path(s) is equal
to or less than a first predetermined value and determining whether the
angle calculated by the calculator 13 is equal to or less than a second
predetermined value, and a changing unit 15 changing a laser process
condition in the circular-arc or linear process path(s) continued to the
two main process paths.

[0051]FIG. 2 is a flowchart showing operation of the controller based on
the present invention. It is assumed that the program of the operation is
stored in a not-shown storage in the controller 10. It is also assumed
that data such as the above-described predetermined values is also stored
in the storage. FIG. 3A is a diagram showing a corner part constructed by
two linear main process paths and a circular-arc path. Hereinafter, with
reference to FIGS. 2 and 3A, the operation of the controller based on the
present invention will be described.

[0052] First, in step S101 of FIG. 2, the analyzer 12 analyzes the process
program 11 to extract a process path. The extracted process path may
include a plurality of linear process paths and/or a plurality of curved
paths. In step S102, the analyzer 12 analyzes whether or not one or more
circular-arc or linear path(s) sandwiched by the two main process paths
exist(s) in the process path. The main process paths may be straight
lines or curved lines.

[0053]FIG. 3A shows, as an example, a corner part constructed by two
linear main process paths ab and cd and a circular-arc path bc. Ends "b"
and "c" of the circular-arc path bc are connected the ends of the two
linear main process paths ab and cd. As a result, the two linear main
process paths ab and cd and the circular-arc path bc form a continuous
process path abcd.

[0054]FIG. 3B shows, as an example, a corner part constructed by two
linear main process paths ab and cd and a linear path bc. In FIG. 3B, in
place of the circular-arc path bc, the linear path bc is shown. As
illustrated, the linear path bc starts from the end "b" and terminates at
the end "c".

[0055] In the case where the circular-arc path bc (or the linear path bc)
exists between the two linear main process paths ab and cd as described
above, the controller 10 advances to step S103. In the case where the
circular-arc path bc or the like does not exist, the controller 10
advances to step S106. In the following, although the case of FIG. 3A in
which the circular-arc path bc is included will be mainly described, the
case of FIG. 3B in which the linear path bc is included is similar to the
case of FIG. 3A.

[0056] In step S103, the analyzer 12 analyzes the shortest length D of the
circular-arc path bc (or the length D of the linear path bc). The length
D is obtained by a known method from the two linear main process paths ab
and cd and the circular-arc path bc which are already obtained and the
process program 11. In step S104, the determining unit 14 determines
whether the length D is smaller than a first predetermined value or not.
It is assumed that the first predetermined value and a second
predetermined value to be described later are preliminarily obtained by
an experiment or the like and are stored in a storage (not shown) in the
controller 10.

[0057] In the case where it is determined that the length D is smaller
than the first predetermined value, the controller 10 advances to step
S105. In the case where it is determined that the length D is not smaller
than the first predetermined value, the controller 10 advances to step
S106.

[0058] In step S105, it can be determined that the corner part of the
process path is relatively small. The calculator 13 virtually extends the
two linear main process paths ab and cd and calculates the angle θ
of a virtual corner part formed by the cross point of the extended paths.
The angle θ is also obtained by a known method from the two linear
main process paths ab and cd and the circular-arc path bc which are
already obtained and the process program 11.

[0059] In step S106, it can be determined that the edge part of the
process path is relatively large. Although not shown, in this case, the
angle formed by the two linear main process paths is calculated by a
similar method.

[0060] In step S107, the determining unit 14 determines whether the angle
θ is smaller than the second predetermined value or not. In the
case where the angle θ is smaller than the second predetermined
value, an edge process operation is instructed in step S108. On the
contrary, when the angle θ is not smaller than the second
predetermined value, a normal cutting process is instructed in step S109.

[0061] The normal cutting process instruction is an instruction which is
output at the time of cutting the workpiece W along the linear main
process path ab or bc, a gentle curve path (not shown), or the like. The
travel speed of the process nozzle 20 is relatively high and the output
of the laser oscillator 22 is relatively large.

[0062] On the contrary, the edge process operation instruction is output
at the time of cutting the workpiece W along a relatively fine path such
as the circular-arc path bc (and the linear path). In the edge process
operation instruction, the travel speed of the process nozzle 20 is lower
and the output from the laser oscillator 22 is smaller as compared with
those in the normal cutting process instruction. In other words, when the
angle θ is smaller than the second predetermined value, the
changing unit 15 changes the normal cutting process instruction to the
edge process operation instruction.

[0063] Each of the travel speed of the process nozzle 20 and the output
from the laser oscillator 22 in the edge process operation instruction is
not constant but is properly changed with time. FIG. 4A is a diagram
showing the relations among time, process nozzle feed speed, and laser
output in an embodiment.

[0064] The horizontal axis in FIG. 4A expresses time, and time
corresponding to the points "b", "c", and "e" shown in FIGS. 3A and 3B is
indicated in the horizontal axis. The vertical axis in FIG. 4A expresses
feed speed of the process nozzle 20 and the output of the laser
oscillator 22. In FIG. 4A, a solid line X1 shows the feed speed of the
process nozzle 20, and a broken line X2 shows the laser output.
Hereinafter, with reference to FIGS. 3A and 4A, the normal cutting
process instruction and the edge process operation instruction in an
embodiment will be described.

[0065] First, in a zone ZA, while moving the process nozzle 20 at a speed
on the one linear main process path ab toward the end "b", the laser
oscillator 22 is driven to make an output. By the operation, the
workpiece W is cut along the linear main process path ab. Toward the end
"b", the speed of the process nozzle 20 is gradually decreased. In a zone
ZB, when the process nozzle 20 reaches the end "b", the process nozzle 20
completely stops, and the laser output is set to zero.

[0066] A zone ZD in which the speed of the process nozzle 20 and the laser
output are zero is a cooling period. By providing such a cooling period,
heat emitted from the laser does not become excessive, and occurrence of
a molten matter (dross) or self burning can be avoided.

[0067] Since the process nozzle 20 is stopped in the cooling period ZD,
the heat from the laser can be prevented from being spread to another
part of the workpiece W. Since the laser output is stopped in the cooling
period ZD, the heat from the laser can be prevented from being
concentrated on the workpiece W. As a result, the circular-arc path bc
which will be described later (or the linear path bc) can be cut
excellently.

[0068] Alternatively, as shown in FIG. 4B as a diagram similar to FIG. 4A,
a piercing period may be provided in which only the process nozzle 20 is
stopped in the zone ZD of the zone ZB to maintain the laser output to a
value smaller than the laser output in the zone ZA and the laser output
at the time of cutting the circular-arc path bc (or the linear path bc).
Generally, when the laser oscillator 22 is stopped completely, power
becomes insufficient, and the output after that may become unstable.
Therefore, it is preferable to provide the piercing period of emitting a
laser beam at low output in a state where the process nozzle 20 is
stopped.

[0069] When the zone ZD is finished, the speed of the process nozzle 20
and the laser output are increased to values smaller than those in the
zone ZA. By the operation, the workpiece W is excellently cut along the
circular-arc path bc (or the linear path bc).

[0070] When the process nozzle 20 reaches the end "c", the time enters the
zone ZC in which the workpiece W is cut along the other linear main
process path cd. As understood from FIG. 4A, it is preferable to set the
speed of the process nozzle 20 and the laser output to be lower than
those in the zone ZA also in a part ce extending from the end "c" along
the linear main process path cd.

[0071] The reason is that, since the travel direction of the process
nozzle 20 changes at the end "c", by setting the speed of the process
nozzle 20 and the laser output to be lower immediately after the change
in the travel direction, the cutting of the workpiece W can be performed
excellently. The part ce is preferably equal to or less than the diameter
D of the circular-arc path (or the length D of the linear path bc).

[0072] Although not shown, also in a predetermined zone just before the
process nozzle 20 reaches the end "b" in the one linear main process path
ab, it is preferable to make the speed of the process nozzle 20 and the
laser output lower than those in the zone ZA for a similar reason.

[0073] After the process nozzle 20 passes through the part ce in the other
linear main process path cd in the zone ZC, the travel speed of the
process nozzle 20 and the laser output are reset to the same values as
those in the zone ZA. After that, the remaining part of the other linear
main process path cd is cut.

[0074] As described above, in the main embodiment of the invention, the
analyzer 12 of the controller 10 analyzes the two linear main process
paths ab and cd and one (or plural) circular-arc path(s) bc (or the
linear path bc) continued to the two paths on the basis of the process
program 11 and grasps the length D. In the case where the length D and
the virtual angle are smaller than predetermined values for the length
and the angle, the changing unit 15 changes the normal cutting process
instruction to the edge process operation instruction.

[0075] In the case where the length D and the virtual angle are smaller
than their predetermined values, it can be determined that the angle
between the two main process paths is considerably small. In the present
invention, in such a case, the laser process condition is changed to the
laser process condition according to the circular-arc process path or the
linear process path. Consequently, in the present invention, even in the
case where a small circular-arc path or a small linear path is inserted
between the two main process paths, while preventing heat emitted from
the laser from becoming excessive, the corner part can be processed
properly. Therefore, a process failure due to occurrence of a molten
matter (dross) or self burning can also be avoided.

[0076] In the present invention, at the time point of generating the
process program 11 which is input to the controller 10, it is not
necessary to analyze the process path. Thus, the process program 11 can
be also generated promptly.

[0077] Hereinafter, with reference to FIGS. 5A to 11, corner parts to
which the controller of the present invention is applied will be
described. FIGS. 5A and 5B are diagrams showing first and second examples
of the corner part. FIG. 5A is almost the same as FIG. 3A and the
circular-arc path bc is inserted between the linear main process paths ab
and cd. The circular-arc path bc is smoothly connected to the two linear
main process paths ab and cd.

[0078] The angle θ of the virtual corner part shown in FIG. 5A is
relatively large and, therefore, the edge process operation is not
instructed. However, in FIG. 5B, the radius of the inserted circular-arc
path bc is small and, therefore, the angle θ of the virtual corner
part is also small. In the case of the process path shown in FIG. 5B, it
is consequently determined that the edge process operation is necessary.

[0079] FIGS. 6A and 6B are diagrams showing fourth and fifth examples,
respectively, of the corner part. Also in the diagrams, the circular-arc
path bc is inserted between the two linear main process paths ab and cd.
In FIG. 6A, the two linear main process paths ab and cd are perpendicular
to each other. In FIG. 6B, the angle formed by the two linear main
process paths ab and cd is an obtuse angle.

[0080] In such a case, even when the radius of the circular-arc path bc is
small, the angle θ of the virtual corner part is large.
Consequently, thermal influence does not occur in the circular-arc path
bc, and the edge process operation is not required. In other words, when
the length D of the circular-arc path bc is small in the cases shown in
FIGS. 6A and 6B, by making determination on the basis of both of the
length D and the angle θ, it is determined that the edge process
operation is necessary.

[0081] FIGS. 7A and 7B are diagrams showing fifth and sixth examples of
the corner part. In the drawings, the circular-arc path bc is inserted
between the curved main process path ab and the linear main process path
cd. As shown in the diagrams, the circular-arc path bc is smoothly
connected to the curved main process path ab. From a cross point "p" of
an extension line of the curved main process path ab and an extension
line of the linear main process path cd, a linear line pq which is in
contact with the curved main process path ab is extended. The angle
formed between the linear line pq and the extension line of the linear
main process path cd is set as the angle θ of a virtual corner
part.

[0082] In FIG. 7A, since the angle θ is relatively small, the edge
process operation is requested as described above. On the contrary, in
FIG. 7B, since the angle θ is relatively large, it is determined
that the edge process operation is not necessary.

[0083]FIG. 8A is a diagram showing a seventh example of the corner part.
In FIG. 8A, the circular-arc path bc is inserted between the two linear
main process paths ab and cd. However, the circular-arc path bc shown in
FIG. 8A is not smoothly connected to each of the two linear main process
paths ab and cd. In FIG. 8A, the angle formed between a tangent line of
an extension line of the circular-arc path bc extended from the point "b"
and the linear main process path ab is set as angle θ1, and the
angle formed between a tangent line of an extension line of the
circular-arc path bc extended from the point "c" and the linear main
process path cd is set as angle θ2.

[0084] In FIG. 8A, the linear main process paths ab and cd and the
circular-arc path bc are not connected smoothly. Consequently, the angles
θ1 and θ2 are smaller than those in the case where the linear
main process paths ab and cd and the circular-arc path bc are connected
smoothly. Therefore, in the case shown in FIG. 8A, the angles θ1
and θ2 are relatively small. As a result, it is determined that the
edge process operation is necessary.

[0085]FIG. 8B is a diagram showing an eighth example of the corner part.
In FIG. 8B, the linear path bc is inserted between the two linear main
process paths ab and cd. As shown in the diagram, the angle formed
between the linear main process path ab and the linear path bc is the
angle θ1, and the angle formed between the linear path bc and the
linear main process path cd is the angle θ2.

[0086] However, in the case shown in FIG. 8B, it is preferable to extend
each of the two linear main process paths ab and cd and set the angle
θ of the virtual corner part. Consequently, by a method similar to
the above, the necessity of the edge process operation can be determined.

[0087] FIG. 9 is a diagram showing a ninth example of the corner part. In
FIG. 9, the circular-arc path bc is inserted between the two linear main
process paths ab and cd. As understood from FIG. 9, the circular-arc path
bc is not smoothly connected to the two linear main process paths ab and
bc. The radius of the circular-arc path bc is much larger than that in
the case where the circular-arc path bc is connected smoothly to the
linear main process paths ab and bc. Consequently, in this case, the
necessity of the edge process operation cannot be determined by the
radius or length D of the circular-arc path bc.

[0088] Therefore, it is preferable to extend each of the two linear main
process paths ab and bc as shown in the diagram, set the angle θ of
the virtual corner part as described above, and determine the necessity
of the edge process operation on the basis of the angle θ.

[0089] FIGS. 10A and 10B are diagrams showing tenth and eleventh examples,
respectively, of the corner part. In FIG. 10A, the circular-arc path bc
is inserted between the two linear main process paths ab and cd. In FIG.
10B, the linear path bc is inserted between the two linear main process
paths ab and cd.

[0090] The circular-arc path bc in FIG. 10A is constructed by two
circular-arc paths bb' and b'c. Similarly, the linear path bc in FIG. 10B
is constructed by two linear paths bb' and b'c.

[0091] In such a case, it is preferable to recognize the continued plural
paths bb' and b'c as a single path bc, not each of the paths bb' and b'c.
Each of the two linear main process paths ab and bc is extended as
described above, the angle θ of the virtual corner part is set as
described above, and necessity of the edge process operation is
determined on the basis of the angle θ.

[0092] In FIGS. 10A and 10B, the length of the path bb' adjacent to the
one linear main process path ab is compared with a predetermined value.
In the case where the path bb' is smaller than the predetermined value,
the path bc including the next path b'c is compared with the
predetermined value. When the path bc is equal to or larger than the
predetermined value, it is preferable to perform the process shown in
FIG. 2. In other words, preferably, the above-described length D is
within a certain range. It is understood that similar process can be
performed also in the case where the path bc is constructed by a
combination of three or more circular-arc paths or linear paths.

[0093]FIG. 11 is a diagram similar to FIG. 4A, showing the relations
among time, process nozzle feed speed, and laser output in an additional
embodiment. In FIG. 11, the solid line shows feed speed of the process
nozzle, and the broken line shows the laser output. The characters shown
in FIG. 11 denote as follows.

[0094] Fa: feed speed in the zone ZA

[0095] Sa: laser output peak value in the zone ZA

[0096] Pa: laser pulse
frequency in the zone ZA

[0097] Qa: laser pulse duty in the zone ZA

[0098] Fb: feed speed in the zone ZB

[0099] Sb: laser output peak value
in the zone ZB

[0100] Pb: laser pulse frequency in the zone ZB

[0101] Qb:
laser pulse duty in the zone ZB

[0102] Lr: condition reset distance (zone
ZD)

[0103] Fr: condition reset speed

[0104] Pr: condition reset laser
pulse frequency

[0105] Qr: condition reset laser pulse duty

[0106] Fc:
feed speed in the zone ZC

[0107] Sc: laser output peak value in the zone
ZC

[0108] Pc: laser pulse frequency in the zone ZC

[0109] Qc: laser pulse
duty in the zone ZC Refer to Table 1 for units of the above items.

[0110] Since the details of FIG. 11 are similar to those described with
reference to FIGS. 4A and 4B, they will not be described. In FIG. 11, the
cooling period or the piercing period ZD is not provided. As shown in
FIG. 11, in the condition reset distance Lr, a laser condition different
from that in the zone ZB, that in the zone ZA, and that at the end of the
zone ZC is set. In FIG. 11, the condition reset distance Lr is provided
only in the zone ZC different from FIGS. 4A and 4B in which the condition
reset distance is provided in the zones ZB and ZC. The condition shown in
FIG. 11 is also included in the scope of the invention.

EFFECT OF THE INVENTION

[0111] In the first and eighth modes, in the case where the linear
distance between the two main process paths or the distance along the
circular-arc or linear process path(s) is equal to or less than a first
predetermined value and the virtual angle is equal to or less than a
second predetermined value, it can be determined that the angle between
the two main process paths is considerably small. In such a case, a
change is made to a laser process condition according to one or plural
circular-arc or linear process paths. Consequently, in the case where a
small circular-arc path or a small linear path is inserted between two
main process paths, the corner part can be properly processed.

[0112] In the second and ninth modes, proper process can be performed even
in a part of the main process path adjacent to the circular-arc or linear
process path(s).

[0113] In the fourth and eleventh modes, the speed of the process nozzle
and/or the output of the laser oscillator are decreased, and heat in the
process part becoming excessive and a process failure occurring due to
occurrence of a molten matter (dross) or self burning can be prevented.

[0114] In the fifth and twelfth modes, the operation of the process nozzle
is temporarily stopped, so that heat from the laser can be prevented from
being spread to another part of the workpiece.

[0115] In the sixth and thirteenth modes, an output of the laser
oscillator is temporarily stopped, so that heat from the laser can be
prevented from being concentrated on the workpiece.

[0116] In the seventh and fourteenth modes, when the laser oscillator is
stopped completely, power becomes insufficient, and a following output
may become unstable, so that it is preferable to provide the piercing
period of emitting a laser beam at low output in a state where the
process nozzle is stopped.

[0117] Although the present invention has been described by using the
above typical embodiments, a person skilled in the art may understand
that the above-described changes, other various changes, omission, and
additions are possible without departing from the scope of the present
invention.